Not sure what stats you are checking, but the wind in September is generally pretty hit and miss, especially further inland. (Many of the windiest days at Sherman in Sept. tend to be hard SW wind, which is pretty sucky to ride.) October is sometimes better closer to the coast, but even worse inland.

Early fall is when the pressure differential between the coast and the valley goes away, it warms up in the bay and cools off in the valley, temps equalize and wind drops off.

That said, summer at Sherman this year was pretty weak IMHO. Folks who teach out in the Delta had their worst year in recent memory. Most weekends ended up being windy, but no way was it windy 7 days a week like it has been the last three years, and alot of the days it was windy, it was just for a few hours am/pm.

yeah, they're a trip! Eventhough seeing them means fall is near, I still love seeing the flocks when they morph around your kite. The birds are the fourth moving element (in addition to water, board, and kite/wind).